Human stem cells are totipotent or pluripotent precursor cells capable of generating a variety of mature human cell lineages. The use of such cells in various therapeutic applications holds promise for clinical applications such as in regenerative medicine and in tissue/organ replacement. Currently, sources of stem cells are limited. Embryonic stem cells, which are derived from embryos, are difficult to produce in significant numbers for practical purposes; current procedures for growth and maintenance in an undifferentiated state of such cells are complex and cumbersome.
Following birth, a mammalian placenta becomes a non-functional organ and is typically discarded. The placenta contains multiple stem cells and other multipotent cells. For example, placenta-derived multipotent cells have been reported to differentiate into mesodermal lineage cells, including adipocytes and osteoblasts; neural lineage cells; and endodermal lineage cells such as hepatocytes.
Umbilical cord blood (“cord blood”) is a source of hematopoietic progenitor stem cells. Stem cells from cord blood are currently cryopreserved for use in hematopoietic reconstitution, a widely used therapeutic procedure used in bone marrow and other related transplantations. Cord blood from a newborn individual is cryopreserved and stored for possible future use in the same individual at a later time. Because the cord blood cells are generally used to treat the same individual from which they were obtained (i.e., the donor and recipient are the same individual), the “donor” cord blood cells have the same human leukocyte antigens (HLA) as the “recipient” individual; therefore, there is no danger of transplant rejection or graft-versus-host disease.
The major drawback of cord blood as a source of stem cells is its small volume, and therefore, limited number of stem cells. A cord blood unit is typically about 100 ml, which is sufficient for successful transplantation only in children, as it contains on average about 2 million hematopoietic stem cells. Transplantation in an adult human generally requires at least 2×105 stem cells per kg, which makes cord blood sample an inadequate source for situations in which higher cell numbers are required.
There is a need in the art for methods for long-term storage of placental tissue; and for improved methods for obtaining ample numbers of stem and progenitor cells from placenta which has been cryopreserved.
Literature
U.S. Pat. Nos. 7,045,148; 7,147,626; 6,059,968; 6,461,645; 7,160,724; U.S. Patent Publication No. 2007/0053888; U.S. Patent Publication No. 2005/0176139; U.S. Patent Publication No. 2005/0058631; U.S. Patent Publication No. 2007/0009880; U.S. Patent Publication No. 2006/0257842; U.S. Pat. Nos. 5,583,131; 7,183,273.